Eyeworld

EW RESIDENTS 122 October 2017 a longitudinal study," uses fMRI to evaluate the neuroadaptive responses of a prospective cohort of 30 patients who underwent bilateral diffractive multifocal IOL implantation. The study builds on recent research by the same group, which analyzed fMRI responses at 3 weeks and found that patients with recently implanted multifocal IOLs had increased activity in areas of the brain responsible for visual atten- tion, cognitive control, and goal-ori- ented behavior as compared to age- and gender-matched controls. 5 The current study provides a more longitudinal assessment, comparing fMRI responses of 30 patients at 3 weeks and 6 months to evaluate the adaptive responses in these areas. The patients were younger than 75 years with less than 6 D of preop- erative sphere, uniform corneal astigmatism less than 1.5 D, and no other ocular abnormalities. As proof of concept, a group of 15 age- and gender-matched controls were included to demonstrate conditions in which no neuroadaptation was expected to occur. Technicians who performed the fMRIs and researchers who evaluated them were masked to patient lens status. The primary outcome was the difference in blood oxygen level fMRI. This information is critical to educate patients that there is often an adjustment period to these new implants. This study illuminated the need to discuss that there are changes occurring not only within the eye, but also within the brain, and that these changes evolve over time. Interestingly, while patients in the study demonstrated a similar frequency of dysphotopic symp- toms after 6 months, the symptoms were statistically less severe and less bothersome. The inclusion parameters in this study were put in place to minimize confounding variables such as ocular abnormalities and high refractive errors in the observation of neuroad- aptation to multifocal IOLs. There- fore, the results in this study may not be applicable to patients older than 75, who may have less po- tential for neuroadaptation as they age. 6 Additionally, these results may not generalize to patients with high refractive errors or ocular abnormal- ities who may in other cases qualify for multifocal IOLs. This prospective study sought to identify neuroadaptation occurring after multifocal IOL implantation, in its stated purpose, to better manage postoperative dysphotopsias and improve multifocal IOL outcomes. While the introduction compares the postoperative dysphotopsias of multifocal versus monofocal IOLs, the study itself compares neuroadap- tivity to a control group without any intervention or history of intraoc- ular surgery (i.e., phakic patients). Prior studies demonstrated that neuroadaptation occurs after refrac- tive surgery, 4 and this study shows that similar adaptation occurs after multifocal IOL implantation. In fu- ture work, it would be interesting to compare adaptivity after refractive surgery to that of standard cataract surgery with monofocal IOLs to that of multifocal IOLs. This would allow us to draw stronger conclusions regarding the adaptivity that occurs uniquely to multifocal IOLs and possibly also compare the presence of positive dysphotopsia with the patient's ability to neuroadapt. Conclusion This longitudinal study is an import- ant addition to the authors' previous work to validate the use of fMRI to evaluate dysphotopsias and neuro- adaptation to dysphotopsias after multifocal IOL implantation. While Wills Eye Hospital residents. Back row: Thomas Jenkins, MD, Lucas Bonafede, MD, Michael Abendroth, MD, Austin Meeker, MD, Jeffrey McMahon, MD, Samir Patel, MD, Aditya Kanesa-Thasan, MD, Tim Arlow, MD; middle row: John David Stephens, MD, Douglas Matsunaga, MD, Ayan Chatterjee, MD, Melissa Sieber, MD, Erin Nichols, MD, Jason Flamendorf, MD, Jordan Deaner, MD, Daniel Ozzello, MD, Martha Ryan, MD; front row: Brett Weinstock, MD, Cindy Zheng, MD, Rebecca Soares, MD, Phoebe Mellen, MD, Michele Markovitz, MD, John Anhalt, MD, Joshua Uhr, MD Source: Wills Eye Hospital dependent (BOLD) values, which follow neuronal activity in the pri- mary visual cortex, with and without glare. The study finds significant- ly higher neuronal activity when subjects were exposed to glare in the early postoperative period (3 weeks). However, at 6 months, glare no longer had a significant association with neuronal activity. This adaptive response at 6 months was supported by psychophysical data: Compared to the early postoperative period, patients at the 6-month visit could detect significantly lower contrast stimuli in the presence of glare. Though no direct comparison was made with the control group, the 15 control patients had no improve- ment in their contrast detection. When asked to detect low contrast stimuli under glare, subjects at 3 weeks had higher activity in the at- tention areas of the brain (cingulate) as compared to 6 months, whereas controls had no significant effort, at- tention, or learning activity on fMRI in either visit. In addition to fMRI outcomes, the study examined changes in patients' subjective symptoms using a questionnaire. At 3 weeks, patients reporting the most bothersome symptoms had significantly higher activation in areas of attention and effort when viewing low contrast stimuli under glare, compared to those with less bothersome symp- toms. By contrast, at 6 months, there was no significant difference in fMRI activity among these two groups. Pa- tients also had statistically less severe and less bothersome symptoms at 6 months compared to 3 weeks. Re- searchers paired this data with func- tional data including visual acuity and reading performance measures. They found a significant improve- ment in both visual acuity and read- ing performance at 6 months versus 3 weeks in the multifocal IOL group. The control group had no such dif- ferences between visits. Finally, the study excluded differences in optical properties of the lenses in patients at 3 weeks and 6 months. Discussion The authors of this study com- bined the objective data of fMRI, reading speed, and visual acuity with subjective changes of both- ersome visual occurrences to draw conclusions regarding neuroadap- tivity and symptom adaptation. The correlation between decreased fMRI signal with increased visual performance and subjective visual improvement suggests that neuro- adaptation may be measurable by Review continued from page 121

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